The present invention is directed to medical articles incorporating absorbent layers, particularly medical articles useful as wound dressings.
Historically, exudate from a wound has been treated by absorbing it using a dressing containing an absorbent material. Typical such dressings contain a padded absorbent material attached to an adhesive tape backing. The padded absorbent material is applied to the wound to absorb the wound exudate. A difficulty with this type of dressing is that the scab typically forms in and as part of the pad as the wound heals. Thus, when the dressing is removed, the scab is removed. This problem has been addressed by providing a porous film between the absorbent material and the wound to reduce the likelihood that a scab formed will become attached to the absorbent material.
More recently the use of so-called “occlusive” dressings for pressure sores and ulcers has gained increasing acceptance. A number of wound dressings of this kind are commercially available. Most of these products are formed from several layers, including at least an inner skin-contacting layer and an outer backing layer. The dressing is applied as a cover for the sore or ulcer in a size providing a margin around the wound area that adhesively seals to the skin. The inner layer contains water-absorptive materials, so that fluid from the wound is absorbed into the layer, making it possible to keep the dressing in place for at least several days. Such occlusive dressings tend to promote healing by maintaining the wound under moist conditions without forming a crust, and serving as a barrier against bacterial infection. Such dressings for “moist wound healing” are particularly useful for dermal burns, traumatic skin deficiencies, incised wounds, and the like.
A wound care product in current use utilizes a hydrocolloid absorbent. Such a material typically has poor transparency so the treatment state cannot be observed from the outside. Also, such a material can partially lose its integrity after absorbing wound fluid. Flexibility of hydrocolloid dressings can be poor, which makes it difficult to apply the dressing to a bend portion of a body, such as a joint, etc. The portion of the absorbent in contact with the wound is converted to a gel-like material, and, when the dressing is removed, a portion of this absorbent material can be left in the wound, and must be removed to permit examination and/or before applying another dressing.
There are known hydrophilic gel materials useful in medical applications such as wound dressings, however, many of them do not have the appropriate balance of absorption and cohesive strength often needed. Thus, additional such materials are needed. Furthermore, it be desirable to provide an occlusive material that is also transparent and flexible for use in a medical article such as a wound dressing or wound packing material.
Another issue that arises in connection with medical articles incorporating absorbent layers is the volumetric expansion of the absorbent materials. When the absorbent layers are attached to, e.g., a backing, expansion of the absorbent layer in directions parallel to the surface of the backing are constrained as the absorbent layer absorbs moisture. As a result, the swelling absorbent layer can stretch the backing and may also pull away from the plane of the skin to form a bubble or a tent above a wound. The swollen wound dressing increases the profile or thickness of the dressing, thus potentially increasing the shearing forces exerted on the dressing by clothing or bedding.